The invention relates to a magnetomechanical converter for relays, which assures the variable adjustment of an outer circuit with a great accuracy in a wide range of the domain of current intensities as well as of voltages of the current supply. The magnetomechanical converter of the invention, which operates with direct current as well as with an alternating current supply, can be used particularly for constructing power relays of high sensitivity and accuracy.
For the solution of different problems related to security, signalizing, or communication, relays are widely used in electrotechnics and in many other types of techniques. The relays are usually constructed in two basic types, as electromagnetic relays and as polarized relays. These devices represent a magnetomechanical converter for converting the energy of a magnetic field to a mechanical energy form for generating a mechanical movement. The relays comprise at least an armature and a unit for generating a magnetic field, wherein the armature and the generating unit are movable relatively to one another.
The electromagnetic relays comprise a pot magnet stator and thereabout an armature which is movably guided and may be coupled with a movement opposing spring. The armature is consisted in general of soft-iron or of other soft magnetic material. The stator forms an electromagnet whose energizing coil is wound on a column of the pot. At the moment when the current reaches a predetermined value, the magnetic field being generated by the coil causes the armature to move: this is the pick-up or the response of the relay. The movement may terminate upon the completion of a switching operation. The electromagnetic relay can be supplied by a direct current as well as by alternating current. Its response follows in a wide range of current intensities surrounding the predetermined current value. The low accuracy of the pick-up can be bettered in the electromagnetic relays of highest quality, i.e. in the protective relays, which have to be produced by a much accurate processing from carefully selected materials, and are relatively expensive.
If the protection relays, e.g. for protection against fire, for protection of property must have a great operating accuracy of the response, they are usually connected with electronic regulating systems. Such solution causes well-known disadvantages, because the electronic circuits have to work together with power circuits. The combination may be too expensive in some cases.
The main characteristics of polarized relays lies in their pick-up at the moment when a current appears in its energizing coil. Pick-up of the relay will be caused by any current, and not only by a current of predetermined value. The basic type of polarized relays contains a movable armature situated between the north and the south poles of a magnetic stator. Either the stator or the armature consists of an electromagnet and the other element is produced from a hard magnetic material. The electromagnet is energized by a direct current. A polarized relay, when supplied by an alternating current, cannot be used for protection--e.g. the electric bell represents this kind of the polarized "relays." The armature of a relay, when the relay is in a standstill position, rests at one of the poles. If a direct current flows through the relay, in the electromagnet the polarity of the poles will be interchanged with one another, and therefore the armature changes its position, moving towards the other pole. This movement may also be of a predetermined extent when the relay is used for switching operations. For regulating the current intensity for relay operation a well-known possibility lies in the use of a spring, but the accuracy of the spring-moved constructions is low. If an accurate regulation must be achieved, the parts of the relay must be processed with high precision and the materials of which they are made should be carefully delected.
A special kind of relays is known from the prior art, namely the TR/S 43 type produced by Siemens Inc., Germany. This relay, which had been widely used in telegraphy, is really composed of two polarized relays. The two electromagnets are situated so that when a current flows through them, their north and south poles lie against one another. The armature is disposed between the electromagnets, and it consists of a long flattened permanent magnet which is polarized parallel to the flat area. The plane of polarization lies parallel or approximatively parallel to a plane containing the north and the south poles of the electromagnet. In the standstill position of the relay and after its operation the armature contacts one of the poles in order to decrease the dispersion of the magnetic flux. The direct current flowing in the electromagnets causes the interchange of the polarity of their poles, and therefore the armature will move from one pole to the other. If the dispersion of the magnetic flux were not so strong, the relay would assure a very good operating characteristics, but the dispersion disturbs the operation and therefore this type of relay is nowadays practically out of the use.
The common characteristic of the above described relays lies in the use of closed magnetic circuits for decreasing the magnetic flux dispersion to a minimal level. In these relays, the work will be assured by energizing either the electromagnet of the stator or the armature, and by the interaction between the armature and the stator. For decreasing the magnetic flux dispersion, the magnetic circuits are so constructed that the magnetic field lines lie in the parts of the magnetic circuit.
A further common characteristic of the known relays and a further limit for their use follows from the unfavorable value of their resetting ratio. It is most desirable that the relay shall return to the starting position immediately when the value of the current has decreased to below the tripping value. The resetting ratio of the known relays can be maximalized at about 80%, instead of the desired 100%. This 80% maximal value can be reached only by specially constructed protection relays produced from selected materials by processing of high accuracy. The commonly used relays are characterized by a much lower value of the resetting ratio than the 80% above mentioned.
By using contactors, thyristors and other similar elements, better operating conditions can be ensured for the relays. This solution has some disadvantages because the use of circuits of different current intensities bring up a number of known problems. Further, the weak current unit has to be equipped by an effective system for protecting against disturbing influences originating in the power circuits.